The invention relates generally to electrical connectors and, more particularly, to a board-to-board connector for transmitting differential signals.
With the ongoing trend toward smaller, faster, and higher performance electrical components, it has become increasingly important for the electrical interfaces along the electrical paths to also operate at higher frequencies and at higher densities with increased throughput.
In a traditional approach for interconnecting circuit boards, one circuit board serves as a back plane and the other as a daughter board or main board. Rather than directly connecting the circuit boards, the back plane typically has a connector, commonly referred to as a header, that includes a plurality of signal pins or contacts which connect to conductive traces on the back plane. The daughter board connector, commonly referred to as a receptacle, also includes a plurality of contacts or pins. When the header and receptacle are mated, signals can be routed between the two circuit boards. In contrast, some electronic devices, such as pluggable transceivers, cable assemblies, and pluggable mezzanine cards, are designed to operate with connections made directly to a circuit board.
The migration of electrical communications to higher data rates has resulted in more stringent requirements for density and throughput while maintaining signal integrity. In addition to density and throughput requirements, there is also a requirement to minimize the size and reduce the complexity of the electrical interfaces.
At least some board-to-board connectors are differential connectors wherein each signal requires two lines that are referred to as a differential pair. For better performance, a ground may be associated with each differential pair. The connector typically includes a number of modules having contact edges that are at right angles to each other.
In one known connector, flat flexible cables are used to interconnect plug-in card slots to a circuit board or host board. Compression connections are used to make the connection to the circuit board. With this design, the user has to line up the flexible cable with a stiffener underneath, and fasten the cable with the compression fitting. The process requires some amount of precision and can be quite tedious.
As the transmission frequencies of signals through these connectors increase, it becomes increasingly important to maintain a desired impedance through the connector to minimize signal degradation. In addition, a ground shield is sometimes provided on the module to reduce interference or crosstalk. Improving connector performance and increasing contact density to increase signal carrying capacity without increasing the size of the connectors remains a challenge.